The present invention relates to a spinning rotor for open-end spinning machines and, more particularly, to a spinning rotor which basically comprises a rotor cup having an annular wall portion defining a rotor opening, a bottom wall portion merging with the annular wall portion, and a mounting hub extending exteriorly from the bottom wall portion, with a rotor shaft affixed to the mounting hub coaxially with the rotor cup.
The requirement for greater and greater productivity has resulted in the development of current open-end rotor spinning machines operating at rotor speeds of well above 100,000 rpms. At such high speeds, special requirements arise as regards imbalance, bearing and stability (danger of bursting) of the spinning rotors.
European Patent Document EP 0 099 490 B1 describes an open-end spinning rotor shaped in a non-cutting manner and with a fiber collector groove to be used at high rotor speeds. In order to avoid the negative effects of centrifugal forces occurring at high rotor speeds such as, e.g., deformation or bursting of the spinning rotor, a bead is formed on the outer circumference of the edge of the rotor cup opening in order to increase the strength. This reinforcement is intended to increase the bursting speed of the rotor.
German Patent Publication DE 197 34 637 A1 discloses a spinning rotor of an open-end rotor spinning machine having a rotor shaft supported in the bearing slot of a support disk bearing arrangement and in an axial bearing which comprises magnetic bearing components. The spinning rotor is intended for rotor speeds of more than 100,000 rpms. This spinning rotor has a distinctly greater wall thickness in the area of the rotor groove or in the area of the greatest outside diameter of the rotor than in the area between the rotor groove and the opening edge. The stability of a body of rotation is increased with a greater wall thickness and any occurring tensions resulting from high speeds can be better distributed. Such embodiments are customary and are frequently used.
Spinning rotors which are reinforced or designed with a great wall thickness in the area of the greatest diameter have absolutely contributed to a certain increase of the speed. However, further increases in speed without losses of function or of safety can not be achieved with these known spinning rotors or can be achieved only in a very limited manner. In particular, problems of imbalance can be produced in that a slight deviation of measurement occurring in the course of the manufacture of the spinning rotor results in the case of rather large diameters or rather large masses in a greater imbalance.